A window function is commonly applied to a signal in order to change the spectrum of the signal. A window function may be used, for example, to suppress side lobes in the spectrum of a signal. Some window functions, such as Blackman, Hanning, and Hamming, have predetermined shapes. Other window functions, including Kaiser, have adjustable or user-defined shapes.
FIG. 1 is a diagrammatic illustration of windowing system according to the prior art. Windowing system 100 includes spatial filter 102 and window function 104. Spatial filter 102 includes a repeating pattern of photodetectors 106, 108, 110, 112. Photodetectors 106, 108, 110, 112 generate individual signals that are grouped and summed 114, 116 to create signals 118, 120, respectively. Signal 118 is typically known as the in-phase (I) channel and signal 120 as the quadrature (Q) channel.
The I and Q channels may have indistinct frequencies, noise, and drop-outs. These factors can make it difficult to interpret the information contained in the I and Q channels. Window function 104 is therefore applied to the channels in order to modify the spectrum of the signals and improve their resolution.